Velocity and Turbulence Measurements for Two Overbank Flow Events in River Severn

Field measurements of velocity and turbulence have been carried out in a study reach of the River Severn at Lower Farm near Shrewsbury during overbank flow. Acoustic Doppler velocity meters have been used for the field measurements of velocity and turbulence, particularly in the interface region between river channel and floodplain. The values of local shear velocity and roughness length for the reach under study were calculated using measured velocity data. The distributions of turbulent intensities, and the Reynolds stresses are also presented. The variation of horizontal shear stress in the vertical direction deviates from linear for the main channel/floodplain interaction region due to the existence of a lateral shear and momentum transfer from the floodplain towards the main channel. Comparisons are made between the field data and previous experimental data from the Flood Channel Facility.